Text legibility in augmented reality with optical see-through displays can be challenging due to the interaction with the texture on the background. Literature presents several approaches to predict legibility of text superimposed over a specific image, but their validation with an AR display and with images taken from the industrial domain is scarce. In this work, we propose novel indices extracted from the background images, displayed on an LCD screen, and we compare them with those proposed in literature designing a specific user test. We collected the legibility user ratings by displaying white text over 13 industrial background images to 19 subjects using an optical see-through head-worn display. We found that most of the proposed indices have a significant correlation with user ratings. The main result of this work is that some of the novel indices proposed had a better correlation than those used before in the literature to predict legibility. Our results prove that industrial AR developers can effectively predict text legibility by simply running image analysis on the background image.

This article addresses some of the challenges involved with creating a stereoscopic video augmented reality “X-ray vision” display for near-field applications, which enables presentation of computer-generated objects as if they lie behind a real object surface, while maintaining the ability to effectively perceive information that might be present on that surface. To achieve this, we propose a method in which patterns consisting of randomly distributed dots are overlaid onto the real surface prior to the rendering of a virtual object behind the real surface using stereoscopic disparity. It was hypothesized that, even though the virtual object is occluding the real object’s surface, the addition of the random dot patterns should increase the strength of the binocular disparity cue, resulting in improved performance in localizing the virtual object behind the surface. In Phase I of the experiment reported here, the feasibility of the display principle was confirmed, and concurrently the effects of relative dot size and dot density on the presence and sensitivity of any perceptual bias in localizing the virtual object within the vicinity of a flat, real surface with a periodic texture were assessed. In Phase II, the effect of relative dot size and dot density on perceiving the impression of transparency of the same real surface while preserving detection of surface information was investigated. Results revealed an advantage of the proposed method in comparison with the “No Pattern” condition for the transparency ratings. Surface information preservation was also shown to decrease with increasing dot density and relative dot size.

Virtual and augmented reality, and other forms of mixed reality (MR), have become a focus of attention for companies and researchers. Before they can become successful in the market and in society, those MR systems must be able to deliver a convincing, novel experience for the users. By definition, the experience of mixed reality relies on the perceptually successful blending of reality and virtuality. Any MR system has to provide a sensory, in particular visually coherent, set of stimuli. Therefore, issues with visual coherence, that is, a discontinued experience of a MR environment, must be avoided. While it is very easy for a user to detect issues with visual coherence, it is very difficult to design and implement a system for coherence. This article presents a framework and exemplary implementation of a systematic enquiry into issues with visual coherence and possible solutions to address those issues. The focus is set on head-mounted display-based systems, notwithstanding its applicability to other types of MR systems. Our framework, together with a systematic discussion of tangible issues and solutions for visual coherence, aims at guiding developers of mixed reality systems for better and more effective user experiences.